How to measure and identify how much compression savings once enabling Sysview for Db2 parameter HISTORY-COMPRESSION=YES

Products

• SYSVIEW Performance Management Option for DB2 for z/OS

Issue/Introduction

How to measure and identify how much compression savings obtained once enabling Sysview Performance Management Option for Db2 for z/OS (IDB2)
parameter HISTORY-COMPRESSION=YES?  What is the average compression benefit?

Resolution

There is no benchmark regarding average overhead usage and space savings from using HISTORY-COMPRESSION=YES option. 

The history files will fill up quicker with compression turned off. The statistics file is low-volume, so the difference will not be noticeable.
The accounting file however is high-volume and will fill up quicker. 

HISTORY-COMPRESSION=[YES|NO] 

Specifies whether to compress the records that are written to the history data sets. SYSVIEW for DB2 uses hardware compression to compress history records,
which generate little CPU overhead. The option can be turned on and off without reallocating the ACCT and STAT files. These files can have both uncompressed
and compressed records mixed in the same file. 

Default: YES 

There are some statistics printed at IDB2 data collector shutdown which will tell you about compression.
Look for the following messages: 

DBG76005I 33566 RECORDS WRITTEN ONTO OUTPUT FILE HSTSTATS
DBG76023I 6 UNCOMPRESSED RECORDS WRITTEN TO FILE HSTSTATS
DBG76024I 69 MB OF DATA COMPRESSED FOR FILE HSTSTATS 
DBG76025I 22 MB COMPRESSED DATA WRITTEN TO FILE HSTSTATS
DBG76026I 67 PERCENT COMPRESSION RATIO OBTAINED FOR FILE HSTSTATS
DBG76027I 152800 COMPRESSION TCB CPU USED FOR FILE HSTSTATS